Effect of sodium restriction on plasma renin activity and renin granules in rat kidney

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Abstract
The relationship between chronic Na restriction and renin content of kidneys at a subcellular level in the rat was studied. Renin granules (RG) were separated by a discontinuous sucrose-density gradient (from 1.2 to 1.7 M) centrifugation. In control rats, RG were mainly recovered in the fractions corresponding to 1.5 M sucrose, whereas most of the mitochondria, lysosomes, and microsomes equilibrated in upper fractions. The RG fraction contained approximately 60% of total granular renin activity. Low Na intake for 4 wk resulted in a 12.4-fold increase in plasma renin activity and led to a 2.6-fold increase in renin activity of the RG fraction. But in Na-restricted rats there was no alteration in the distribution pattern of renin activity on sucrose-density gradients, indicating that there was no change in the density of RG. Increased renin activity appears in storage granules following chronic Na restriction.